Benjamin F. Dattilohttps://works.bepress.com/ben_dattilo/Recent works by Benjamin F. Dattiloen-usCopyright (c) 2019 All rights reserved.Sat, 05 Oct 2013 07:00:00 +00003600Revising Rafinesquina: new insights on a familiar fossilhttps://works.bepress.com/ben_dattilo/33/Benjamin F. DattiloSat, 05 Oct 2013 07:00:00 +0000https://works.bepress.com/ben_dattilo/33/PresentationsThe Orientation of Strophomenid Brachiopods on Soft Substrateshttps://works.bepress.com/ben_dattilo/14/<p>Strophomenid brachiopods have long been interpreted as ‘‘snowshoe’’ strategists, with their flattened concavoconvex valves providing resistance to foundering in very soft sediments. There has been a sharp difference of opinion in whether the shells were oriented with their convex or their concave surface in contact with the sediment. This study, along with independent evidence from sedimentology, ichnology, and morphology, indicates that the strophomenids lived with their shells concave down (convex up). Experiments indicate the force required to push shells into soft cohesive muds is much greater for the convex up than for the convex down orientation. Forces also increase with shell curvature. All measured forces greatly exceed estimates of the downward force exerted by the weight of the shell, indicating that foundering resistance may not have been the key functional requirement. Instead, a convex up orientation would have provided resistance to overturning in currents, in particular if the valves gaped widely. The ‘‘snowshoe’’ may not be the relevant paradigm for the shell morphology of these forms. An alternative is that they functioned more as a tip-resistant base, similar to those of garden umbrellas or stanchions.</p>
Sun, 01 Sep 2013 07:00:00 +0000https://works.bepress.com/ben_dattilo/14/ArticlesThe Curse of Rafinesquina: Negative Taphonomic Feedback Exerted by Strophomenid Shells on Storm-Buried Lingulids in the Cincinnatian (Katian, Ordovician) Series of Ohiohttps://works.bepress.com/ben_dattilo/31/<p>Thousands of lingulid brachiopods were found clustered beneath hundreds of individual valves of the strophomenid brachiopod Rafinesquina in the Upper Ordovician of Ohio. This association suggested a relationship between the two brachiopods, but the nature of this relationship was unclear. We utilized serial thin sectioning to examine these brachiopods and to determine the origin of the bed in which they were found. Sedimentary structures, mixed taphonomies, and stratigraphic and paleogeographic setting suggest that the lingulids occupied a hiatal concentration that had previously been reworked, but not significantly transported, by tropical storms. The final burial event was a storm that exhumed living lingulids along with disarticulated Rafinesquina shells from the same sediments. Neither living nor dead shells were transported, but were reworked locally, then reburied together. The lingulids then burrowed upward to escape, but most were trapped by the concavedownward Rafinesquina shells that had been redeposited above them. This finding offers the first documented example of negative ecosystem engineering and taphonomic feedback in the fossil record, as well as the oldest documented lingulid escape traces. It also suggests that taphonomic feedback can be subdivided into live-dead interactions that occur under normal background depositional conditions and those that occur during periodic short-lived sediment-reworking events, such as storms and tsunamis.</p>
Sat, 01 Jun 2013 07:00:00 +0000https://works.bepress.com/ben_dattilo/31/ArticlesRevising Rafinesquina: new insights on a familiar fossil.https://works.bepress.com/ben_dattilo/10/Wed, 23 Jan 2013 08:00:00 +0000https://works.bepress.com/ben_dattilo/10/PresentationsOccurrence and Features of Dinosaur Trackways of the Paluxy River Valley (Lower Glen Rose Formation, Lower Cretaceous), Somervell County, Texashttps://works.bepress.com/ben_dattilo/26/Tue, 01 Jan 2013 08:00:00 +0000https://works.bepress.com/ben_dattilo/26/PresentationsTHE “CURSE OF RAFINESQUINA:” NEGATIVE TAPHONOMIC FEEDBACK EXERTED BY STROPHOMENID SHELLS ON STORM-BURIED LINGULIDS IN THE CINCINNATIAN SERIES (KATIAN, ORDOVICIAN) OF OHIOhttps://works.bepress.com/ben_dattilo/1/<p>Taphonomic feedback is the idea that accumulation of organic remains either enhances the habitat for some organisms (positive taphonomic feedback), and/or degrades the habitat for others (negative taphonomic feedback). Examples of epibionts living on skeletal remains are direct evidence of positive taphonomic feedback. Disruption of infaunal burrowing activities by skeletal fragments is an example of negative taphonomic feedback; direct fossil evidence of this phenomenon has not been documented previously. Infaunal organisms are vulnerable to exhumation or entombment during storms, but organisms that burrow can also re-establish viable life positions subsequently. For example, when modern lingulids re-burrow after exhumation, they first dig downward and then turn upward, forming a U-shaped burrow. If entombed, they burrow upward. Lingulid escape burrows previously documented date only to the Triassic, and, like modern lingulids, appear to have been restricted to fine siliciclastic sediments. In contrast, an Upper Ordovician occurrence from Ohio contains hundreds of articulated cf. Pseudolingula sp. clustered beneath dozens of disarticulated, concave-down Rafinesquina shells in a storm-reworked shell gravel. Serial sectioning reveals the complex burrows of these lingulids deflecting around shell-fragment obstacles. Burrows also show that when the lingulids encountered the Rafinesquina valves, they followed the concave surface upward toward the highest point, thereby lodging themselves beneath the domed shell. The entrapment of cf. Pseudolingula sp.beneath Rafinesquina demonstrates that lingulid brachiopods have long had the ability to burrow upward and re-establish themselves after burial by a storm event, and is direct evidence of a negative taphonomic feedback mechanism by which infaunal escape behaviors were rendered ineffective by the presence of skeletal debris.</p>
Rebecca L. Freeman et al.Tue, 01 Jan 2013 00:00:00 +0000https://works.bepress.com/ben_dattilo/1/ArticlesTempestites in a Teapot? Condensation-Generated Shell Beds in the Upper Ordovician, Cincinnati Arch, USA.https://works.bepress.com/ben_dattilo/5/<p>Skeletal concentrations in mudstones may represent local facies produced by storm winnowing in shallow water, or time-specific deposits related to intervals of diminished sediment supply. Upper Ordovician (Katian) of the Cincinnati region is a mixed siliciclastic-carbonate succession including meter-scale cycles containing a shelly limestone-dominated phase and a mudstone-dominated phase.</p>
<p>The “tempestite proximality model” asserts that shell-rich intervals originated by winnowing of mud from undifferentiated fair-weather deposits. Thus shell beds are construed as tempestites, while interbedded mudstones represent either fair-weather or bypassed mud. Meter-scale cycles are attributed to sea-level fluctuation or varying storm intensity.</p>
<p>Alternatively, the “episodic starvation model” argues, on the basis of petrographic, taphonomic, and stratigraphic evidence, that, despite widespread evidence for storms or other turbulence events (e.g. tsunamis), winnowing alone could not generate shell beds where none had previously existed. Instead, variations in sediment supply are construed as the principal cause of shelly-mudstone cycles. Shell-rich deposits accrue during periods of siliciclastic sediment starvation and relatively shell-free mud accumulates during periods of sediment influx.</p>
<p>Tempestite proximality and episodic starvation models lead to contrasting predictions about proximal-to-distal facies patterns. These are: (i) large versus small volumes of distally-deposited, bypassed mud; (ii) proximal grainstones and distal packstones versus distal grainstones and proximal packstones; and (iii) proximal versus distal amalgamation and condensation of shell beds.</p>
<p>In this paper, these predictions are tested by (i) comparing meter-scale cycles from different horizons and depositional environments through the lower Cincinnatian succession (Kope through McMillan Formations representing deep subtidal through intertidal environments), and (ii) correlating intervals and individual meter-scale cycles from the Fairview Formation of the Cincinnati Arch (shallow subtidal) north and west into the Maquoketa Shale (deep subtidal) in subsurface of Ohio and Indiana. Both approaches show patterns consistent with episodic starvation, not winnowing, including: (i) small differences in stratigraphic thickness indicate small volumes of bypassed mud; (ii) discrete distal deep-water grainstones that splay proximally into bundles of thinner shallow-water packstones alternating with shelly muds show that grainstones formed from a lack of, rather than removal of mud; and (iii) distal shell bed amalgamation and condensation (and corresponding proximal splaying) of shell beds shows a proximal source of mud.</p>
<p>Thus, winnowing by storms or other turbulence events did not generate shell beds or cycles from undifferentiated sediments despite abundant evidence for storm deposition. High-resolution correlations imply that the shell-bed and mud-bed hemicycles reflect simultaneous basin-wide changes in sedimentary style rather than contemporaneous facies belts that track sea-level. In this sense, shell-rich and mud-rich hemicycles are “non-Waltherian” facies.</p>
Sat, 15 Dec 2012 08:00:00 +0000https://works.bepress.com/ben_dattilo/5/ArticlesThe Layer Cake Paradox: How Did Patchy Environments Become Uniformly Layered Sediments in the Ancient Marine Deposits of Cincinnati?https://works.bepress.com/ben_dattilo/28/Benjamin F. DattiloMon, 03 Dec 2012 08:00:00 +0000https://works.bepress.com/ben_dattilo/28/PresentationsMicrostratigraphic Analysis of Burrow-Reworked Dinosaur Track Bed at Joanna's Track Site, Cretaceous Glen Rose Formation, Glen Rose, Texashttps://works.bepress.com/ben_dattilo/44/<p>Although dinosaur trackways are common in the Cretaceous Glen Rose Formation of Texas, the recently discovered Joanna track site illustrates a unique ichnological relationship where dinosaur tracks were disrupted by invertebrate burrows made long after burial. In an effort to document the precise sequence of events, we described the interval from 0.3 m below the track layer through 2.7 m above it in a vertical outcrop adjacent to the track site, focusing on the 70-cm of strata immediately above the track horizon. An 8-meter N-S cross-section of this 70-cm interval was power-washed, examined for trace fossils, body fossils, and lithology in the field, and the interval sampled as a hand-cut 2-piece 20 cm square core. To prevent disintegration, the rock was coated in epoxy as it was removed. The lower piece was dry cut into a few 3-4 cm thick vertical slabs; the upper part will be prepared similarly. These are to be dry sanded and polished to reveal microstratigraphic details. A continuous series of thin sections will also be made through the thickness of the sample.</p>
<p>The track layer contains burrows of at least two ichnogenera, <em>Arenicolites</em> and <em>Thalassinoides</em>. The former is restricted to the track layer, whereas <em>Thalassinoides</em> originates in two generations, one before formation of the <em>Arenicolites</em> and another from the top of a highly bioturbated 30 cm bed of ostracod and foraminifera-rich mud overlying the track surface. This layer contains unidentified crustaceans, a turtle shell fragment, shark teeth, and small vertebrae. Capping this is a thin bed of pyritic mud; 20 cm of burrowed mud with bivalves in life position and<em> Planolites; Thalassinoides </em>(near top, filled with grainier sediment); and <em>Teichichnus </em>(spreiten showing retrusive movement). A 20 cm grainstone bed tops the interval. Beneath the tracks, the track layer wackestone grades into 20 cm of ostracod packstone with mud-filled burrows.</p>
<p>An upward increase in mud and deeper water fauna suggests a transgressive succession, and the burrowed mud bed overlaying the tracks suggests episodic burial events. Relationships between tracks and traces suggest that <em>Thalassinoides</em> and <em>Arenicolites </em>tracemakers colonized the track layer prior to the creation of tracks, then the second generation of <em>Thalassinoides</em> formed after burial of the dinosaur tracks by at least 30 cm of mud.</p>
Tue, 06 Nov 2012 08:00:00 +0000https://works.bepress.com/ben_dattilo/44/ArticlesHigh-Resolution Correlation and Sedimentology of Carbonate-Shale Cycles in the Type Cincinnatian (Upper Ordovician; Katian): Implications for a Revived "Layer Cake Stratigraphy"https://works.bepress.com/ben_dattilo/15/<p>Strata of the type Cincinnatian Series form an exemplar of the denigrated notion of “layer cake stratigraphy”; Edward Oscar Ulrich, founder of the “Cincinnati School” of paleontology (ca. 1910s), argued that the stratigraphic record is composed of stacks of continuous, far-traceable layers. This view was fostered by observations of limestone-shale strata, then-exposed on the hillsides and riverbanks of Cincinnati. Subsequently, most geologists rejected this notion and favored a “mosaic” view of strata as local patches, based on studies of modern marine environments. Cincinnati reference sections such as those of Eden and Fairview Parks are now largely overgrown or under concrete. However, new construction has provided sections far more complete than the original outcrops, which demonstrate nearly bed-for-bed matches over the outcrop region and into the subsurface.</p>
<p>Moreover, the typical assumption that shell rich limestones were produced by intervals of local storm winnowing is rejected based on a variety of data: a) limestone bundles splay up-ramp and become highly condensed down-ramp; b) many beds are not winnowed and may contain micritic matrix; c) shell concentrations of background sediments demonstrate that formation of shell beds by winnowing alone would require removal of 10s of meters of mud; d) mudstones also show abundant storm deposition/erosion features; e) shell-rich limestones are associated with concretions and hardgrounds suggesting sediment starvation. A model involving periodic sediment starvation, coupled with storm processing better explains these observations. These findings are of key importance in: a) establishing new, well-documented reference sections for the type Cincinnatian; b) providing a resounding counter to the “mosaic” view and re-establishing a very detailed “layer-cake”; and c) providing data for an evolving view of the stratigraphic record as the response to widespread climatic/sea-level cycles and regional scale catastrophes.</p>
Tue, 06 Nov 2012 08:00:00 +0000https://works.bepress.com/ben_dattilo/15/Presentations